Method and system for refrigeration of railroad cars



R. D. PIKE 2,641,110

METHOD AND SYSTEM FOR REFRIGERATION 0F RAILROAD CARS June 9, 1953 5sheets-sheet 1 Filed Aug. l0, 1950 5 Sheets-Sheet 2 R. D. PIKE |,i IIN:.l.l In. Qlillll June 9, 1953 Filed Aug. 1o, 195o IN1/EN TOR. ROBERT D.lo/KE Arran/sys June 9, 1953 R. D. PIKE 2,641,110

METHOD AND SYSTEM FOR REFRIGERATION OF' RAILROAD CARS Filed Aug. 10

uNKr-:n TEMPERATURE 'F 1950 5 Sheets-Sheet 3 I I I I I I I I NUMBERSINDICATE LB NH4 NO3` PER IOO LB ICE I I I 2O O 5 IO I5 2O 25 50 35 LB NACL PEE |00 LB ICE INVENTOR. R085@ T D. P//IE ATTORNEYS Patented June 9,195g METHOD AND SYSTEM FOR REFRIGERA- TION F RAILROAD CARS Robert D.Pike, Greenwich, Conn.

Application August 110, 1950, Serial No. 178,603

17 Claims.

This invention is directed to an improvement in method and apparatus forrefrigerating the storage compartment of a railroad refrigerator car.

Another object of the present invention is to provide a more economicaland eiiicient refrigeration system in a railroad refrigerator carwherein the refrigerants are disposed solely in the ceiling of the carand wherein substantially the entire horizontal door area of the car isavailable for lading purposes in contrast to those refrigerator carswherein vertically extending end bunkers sometimes occupy more than tenpercent of the available lading area.

Another object of this invention is to utilize in eflicient andeconomical manner the refrigerant properties of a eutecti-c mixture ofsodium chloride, ammonium nitrate or other melting point depressants,and ice disposed in spaced overhead tanks.

Other objects and advantages of my invention will become apparent fromthe following description of .a preferred form of the invention,reference being made to the accompanying drawings wherein Fig. l is alongitudinal section of my refrigerator car taken along the middle ofthe car;

Fig. 2 is a fragmentary plan View taken on the line 2-2 of Fig. 3;

Fig. 3 is a View in section taken substantially on the line 3-3 of Fig.1, but on a larger Yscale;

Fig. 4 is a fragmentary View in section taken on the line 4 4 of Fig. 1,but on a larger scale;

Fig. 5 is a chart showing tank temperatures with various mixtures ofwater ice, sodium chloride and ammonium nitrate;

Fig. `t is a fragmentary View in section taken on the line t-t-of Fig.V1; and

Fig. 7 is a fragmentary view in section taken on the line T-l' of Fig.1.

In United States Letters Patent No. 2,501,141, there is shown arefrigerated railroad car suits able for the transportation of frozenfoods or the like at uniform and predetermined low tem-V peratures. Thestorage compartment of the car there shown was spaced from the innersurfaces of the car to provide air passageways therebe`- tween. Apositive circulation of air was provided to effect a symmetrical patternof transverse and longitudinal, peripheral flow lof air about thestorage compartment in cooperative heat transferrelationship vvith aplurality-of low temperature refrigerant bunkers.

in Patent No. 2,501,141, the circulating .air contacts in heat exchangerelationship ,end refrigerants of Water ice and salt mixture. The

end refrigerants in the embodiment shown were air permeable ice bedshaving interstices providing numerous air passages through the bed andgiving large surface areas for transfer or" heat from air to ice toallow for the transfer of the latent heat of melting. The circulatingair also contacts overhead tanks containing Dry Ice or low temperatureeutectic brine mixtures in heat exchange relationship of predeterminedcharacter.

Through the use vof the invention hereinafter described, I am able toreduce very considerably the cost of transcontinental shipment ofrefrigerated food and the like by (-1) increasing the amount of ladingarea and the eiliciency of the refrigerant system, (2) proportionatelyreducing the cost of refrigerants, and (3) by providing in the system aexibility of temperature range relative to refrigerant used heretoforeunachieved.

Referring now to the drawings, l have shown one form-of my inventionembodied in a railroad car IIJ adapted to transport frozen foods or thelike in the desired temperature range from about 0 F.5 F. with certainrefrigerant mixtures, or in other ranges with other refrigerants.

The car l- .comprises a top Il, sides B2, ends I3 and bottom I4, all ofthe car walls being insulated in a suitable-manner. The storage area orcompartment proper of the car extends substantially the entire lengthand width of the car. The usual loading doorways I5 are provided in thesides I2.

The floor 20 of the storage compartment may be formed of fioor rackscomprised of planks 2| six to eight inches wide mounted on suitablesupports 22 which space the rack about six inches above the bottom I4 ofthe car thereby forming an air chamber 23 between the iioor 251 andbottom I 4. The planks may be Aspaced an inch or two apart to provideair communication between the storage compartment and air chamber 23.

The ends IS `and the `sides i8' of the storage compartment are formed bysecuring plywood panels or boards to nailing studs (not shown) attachedto the inner surfaces of the car, thus providing together with the floor2G, a storage compartment shell Within the confines of the car.

The ends i6 of the storage compartment are preferably spaced about 5 to6 inches from the inner surfaces of the car ends i3, thereby forming a,vertically extending end i'lue 26 -that is in communication with airchamber Z3 as shown in Fig. 1. The side walls llt of the compartment arealso spaced from the inner surfaces of the car sides ("2 to provide sidewall nues 28 about an inch wide as shown in Figs. 4 and 6. These flues28 are similarly in communication with air chamber 23 as may be seen inFig. 6. These side wall fines 28 are disposed in the wall portion of thecar located between the dotted lines shown in Fig. 1.

Beneath the compartment floor near the ends of the car are provided fans30 which are activated by the car axle through connections not shown.There is no spacing between the planks which make up the oor rack in theportion of the latter' which extends from the fans to the compartmentend I6. Between the fans the air chamber 23 is in communication with thesidewall ues 2S as shown in Fig. 6.

Beneath the roof of the car at spaced intervals a plurality of overheadrefrigerant tanks 36, 38, 40 are provided, the disposition of which isshown in Figs. 1 and 2. Each of' these tanks is comprised of an opensheet metal container 3I secured to the top of the car by appropriatemeans as by brackets 32, with the opening of the tanks being inalignment with `a pair of hatches 33. The container structures of thetanks extend substantially transversely of the car as is apparent inFig. 2 and they may be supported at opposite ends by bracket and angleiron assembly or other suitable means.

On the bottom plates of the various tanks are provided metal tansfer ns34 welded to the tanks, and being preferably about 11/2 deep, and on 3"centers. These ns extend transversely of the length of the car on thecentermost pair of tanks 36 and on the intermediate pair of tanks 38.The fins may be omitted for a short distance 39 at the center, asindicated in Fig. 4. The bottom plates of the end tanks 40 are providedwith similar fins, except that, as indicated in Fig. 1 and 3, these nsextend parallel to the longitudinal axis of the car.

Disposed beneath the overhead tanks are drip boards or sub-ceilingpanels 42 and 42a, as shown in Figs. l, 3 and 4. It will be noted thatthe drip boards extend to and are secured upon the upper ends of theside wall panels I8 of the storage compartment. The drip boards 42 slopetoward the car ends so that any moisture which may accumulate will, uponmelting, flow down through the car end flues 26 and be discharged fromthe car in suitable manner so as not to wet the goods in thecompartment. These drip boards 42 preferably extend under the firstencountered intermediate tanks 38, although they may be terminated shortthereof, extending only so far as the inner edges of the end tanks 40.Beneath the centermost tanks 36 the drip boards 42a preferably slopefrom the car center toward each side so that ice which may accumulate onthem or beneath the tanks will, upon melting drain into side wall flueopenings 28 as described hereinafter.

Opposite the ends of the centermost and intermediate pair of tanks 36and 38 are openings 44 into the side wall fiue area 28 which aresubstantially equal in length to the full width of the tanks along thelength of the car as shown in Figs. 2 and 4. In addition to theseopenings, I preferably provide two smaller openings 46 into the sidewall lues in the region of the doors I on both sides of the car, andalso opemngs 48 of about the same size as those in the door region intothe side wall flues, the latter openings being located intermediate thetanks 38 and 40 as shown in Fig. 2. These openings 44, 46, and 48, takentogether, are suicient in size to handle the volume of air flownecessary for the predetermined proper circulation of the car at avelocity through them which will be adequate to evenly distribute theflow of air into the side wall flues as Will be described furtherhereinafter.

Between the insulated end walls I3 of the car and the outer ends of theend tanks 40, and between the side walls of these tanks and the insideof the insulated walls I2 of the car are provided spaces or flues 5D and52 respectively. Similarly, there are provided spaces or nues 54 betweenthe ends of the tanks 36 and 38 and the side walls I2 of the car. Theprovision of these flues 50, 52 and 54 permits the circulating `air tocontact the maximum surface area of the tank for heat transfer purposes.

Interconnecting the tanks 36, 38, and 4D, and extending from thecentermost tanks 36 longitudinally to the ends of the car, as shown inFigs. 1 and 2, are a plurality of overflow pipes 56 and 56a adapted todrain brine accumulating in the center tank 36 through the pipes 56 tothe tanks 38 and finally through pipes 56a. to end tanks 40. Overilowsdrains 56D lead from the end tanks 40 vertically down through the endflues 26 so that the brine may eventually be drained out of the carthrough a suitable connection not shown in detail.

For effective and economical operation of my invention in thetransportation of frozen foods l for example which are preferablymaintained at a temperature of not over 5 F. or even lower,approximating 0 F., I prefer to provide refrigerants of the followingkind in the tanks. The end bunkers 40 and intermediate bunkers 38 arefilled through the hatches with the eutectic mixture of water ice andsalt, namely pounds of ice to 30 pounds of salt. This mixture in itselfgives a brine temperature of about 5 F. The center bunkers 36 are filledwith a eutectic mixture of sodium chloride, 30 pounds, and ammoniumnitrate, 15 pounds, to each 100 pounds of ice, thereby establishing inthese bunkers a temperature of about -15 F. This temperature'will beexplained by reference to the chart in Fig. 5.

The air circulation pattern of the car may now be easily explained inview of the description of the car structure set forth above. The fans30 draw air from the air chamber 23 toward each end of the oar indivergent streams and direct the air longitudinally beneath thecompartment floor into the end flues 26 and upwardly into contact withthe outer surfaces of end tanks 40. The air substantially envelops theends and sides of these tanks through the flues 50 and 52, with themajor part of the air being constrained by the drip boards 42 to flow inheat transfer relation with the bottom plates and heat transfer ns ofthe tanks. The then convergently directed air streams at each end of thecar are channeled by means of the drip boards 42 into contact with theoverflow pipes 56a, against the side walls of the next tanks 38, andbeneath these tanks into contact with the heat transfer ns and bottomplates of the tanks, and between the drip boards and the tank bottoms.

From the air streams between the end tanks 40 and the tanks 38 Ipreferably introduce about 15% of the total stream into the side wallopenings 48 leading into the side wall ues. It will be noted that theopenings 48 are located at a position which will lead the air throughthe side wall fiues into the fan inlets. About twice this amount of airis diverted into the larger openings 44 disposed adjacent the ends ofthe bunk'- ers 38.

The balance of the converging air streams next contact the overflowpipes 56 and then come into heat exchange relationship with the tanks 36as was described in connection with tanks 38. A similar amount of thestreams is diverted into the openings d adjacent the ends of these tanks36. The balance of the air streams is diverted into the openings 46 inthe region of the door by the time it reaches the center of the car.Some air, of course, may be deflected into the storage compartment.

The average velocity of air in all of the openings into the side wallflues is made high enough so as to insure a substantially equal velocityin each, which in turn insures an even distribution of the iiow from oneend of the car to the other. It will be noted that the iiow of air inheat transfer relation with the bottom plates of the center andintermediate tanks is a combination of iiow across the heat transferfins and along them transversely to the openings into the sidewalliiues, which insures a high coeflicient of heat transfer expressed as B.t. u./s. f./hr./F. difference between the air and the surfaces. Inaddition, both sides of the tanks come into efficient heat transferrelation with the moving air and with the plurality of overflow pipes56, 56a. These pipes add a not inconsiderable additional surface forheat transfer.

Thus, substantially all of the circulating air passes through theopenings into the side wall flues, and from these into the air chamber23 beneath the floor of the compartment, then back into the fan inletsfor recirculation over the same path as just described.

The result of this circulation is to effect a highly efficient transferof heat from the air into the refrigerants in the top tanks and tosubstantially completely envelope the goods with this chilled air. Thus,almost all of the heat which flows into the car from the outside isbrought into the circulating air and conveyed in it to the refrigerantswithout there being any` opportunity for the heat to flow directly intothe goods within the storage compartment. The shielding air streamsfollow a course along the length of the car toward the center, withsimultaneous ydiversions of the air into the side Wall lues andvertically down to the air chamber 23 beneath the compartment floor andthen move divergently toward the fan inlets which are near the ends ofthe car.

Considering now the use of the refrigerants in the tanks, it will beclear that as the ice in the mixture in the center bunkersr 36 melts,the brine will flow through the overflow pipes toward the opposite endsof the cars and into the intermediate tanks 38. By the use of aplurality of overflow pipes 56, the strong ammonium nitrate brine fromthe center tanks is evenly distributed and thoroughly mixed in theadjacent tanks 38. Because no ammonium nitrate is added directly tothese latter tanks, the concentration of ammonium nitrate in the brinewhich flows out through the plurality of overflow pipes 56a will belower than in the pipes 56, and will be, in turn, uniformly mixed in theend tanks 40, giving a slight further rise in temperature of the brinein these end tanks as compared with the tanks 38.

Thus the overflow of the brine from the center most tanks 36 into andthrough the tanks 38 and 40 provides a diminishing concentration ofammonium. nitrate,y but this. concentration.1 nevertheless, is vsuicientinupractice to reduce 'the term perature in the end tanks 40 Ato about-12"`F which, as indicated by the chart in Fig. 5, necessitates about vepounds of ammonium nitrate per pounds of ice, with thirty pounds ofsalt. This is substantially the composition of the brine which drainsfrom the car through the overiiow pipes 56h, which is economical in theuse of ammonium nitrate and which gives an average temperature to theheat transfer surfaces of all of the top tanks of about 13 F.

The active circulation of the air which has been described hereinabovein contact with the heat transfer surfaces of the tanks, in View of the.fact that the average temperature of the brine in these `tanks may bemaintained, by the means described, at approximately 13 F. makes itpossible to deliver frozen foods after transcontinental hauling in thesummer season from this car at about 0 F. or less.

It is believed that .the combination of center, intermediate and endoverhead tanks having a diminishing temperature from the center to theend, together with a forced circulation of air in series from the endtoward the center in heat transfer relation with the tanks, is broadlynew in the refrigeration art. By means of my invention there isestablished in the car a low, uniform temperature in the goods even inthe hottest summer weather.

Other refrigerant mixtures can be used in the tanks than the combinationdescribed above, and many of the novel features of my invention can beachieved thereby except that the temperature of the goods upon deliverywill vary from the temperature range above given. For example, if all ofthe tanks are filled with eutectic mixture of sodium chloride and waterice, the refrigeration of the car will be equally effective except thatthe temperature of the goods will range at from 5 to 8 F. upon delivery.Similarly, if it is desired to utilize the car of my invention fortransportation of perishables, which should not be held at temperaturesmuch, if any, below 34 F., I may supply water ice alone to all of thetop bunkers.

Example In understanding the principles and operation of my invention,the following illustration may be helpful. This example refers to theapplication of my invention to a superinsulated car with 6-7" insulationand having an overall length of 45 1". There are four intermediate toptanks, 31%" wide (along the length of the car) and 8 6" long (across thecar) by about 1'1" deep, and one end top tank on each end, 48 wide(along the length of the car) by about 8 6 long, and having a depth ofabout 11". In an average transcontinental crossing in the summer withtime in transit under load of about 183 hours, the consumption of Waterice en route will be about '28,700 lbs. in order to deliver the goods atabout 0 F. in the car of my invention.

The following table summarizes the consumption of refrigerants en routeand discardedat the end:

Average temperature brine inltop taiilsend top tanks 12 F., two centertop tanks -15 13 F. Average temperature air circulating in heat transfercontact with surface of top tanks -4. 16 F Average temperaturedifference between outside air and air inside car 78.6 F. Total flow ofheat into car, B. t. u./hr 14, 100

Heat estimated as passing directly into refrigerants through the roof ofthe car, B. t. u.'/hr Heat which must pass through plate surfaces oftanks,

14,1oo-2,o3o, B. i. 11./hr 12, 07o Areas available for heat transfer:Bottom plates of intermediate tanks, in-

cluding heat transfer fins 180. 85 s. f. Side plates 45. 3 s. f. Bottomplates end tanks with heat transier ns 135. 6 s. f. Area side and endplates 33. s. f.

`Total Temperature difference between brine and circulating air,13-4.176= v 84 F.

Heat transfer coefficient, B. t. u./s. f./hr./ F.,

394.85X8.84 `"'f v Velocity of air entering openings into side wallflues, feet/ second .-5 7 z... 14.7

Pressure corresponding inches water gage, m .0510

Thepressure imparted by the fans at train speed of 31.4 M. P. H., isabout .21" W. G. The fans therefore produce sufficient pressure in theiroutlets to circulate the air and Vto provide the velocity ofentrance'into'A thev tops of the side wall fiues. At the same time, thevelocity of en trance into the side wall flues is high enough todistribute the ow'of the air to the center of the car and thence backunder the floor racks to thefan inlets;

I wish it to be understood that I do not confine myself to the precisedetails herein set forth in the preferred means of carrying out my indvention as it is apparent that many changes and variations may be madeby those skilled in the simultaneously passing the streams into a plu#rality of heat exchange zones wherein progressively diminishingtemperatures chill the air,

and diverting successive predetermined portions I of the convergent airstreams transversely and peripherally whereby substantially all the airof each stream is thus peripherally distributed prior to convergence. Y

2. In a method of refrigerating the storage compartment of arefrigerator car wherein air is drawn transversely about the side wallperiphery of the storage compartment, then withdrawn to each end of thecar in divergent streams, and circulated vertically about the ends ofthecar, the steps comprising directing the thus circulated air streamsconvergently above the storage compartment and simultaneously passingthe streams into a plurality of heat exchange zones of progressivelydiminishing temperatures to chill the air, and drawing off, transverselyand peripherally, predetermined portions from the convergent air streamsat spaced intervals whereby each stream is thus substantiallydistributed peripherally prior to convergence.

3. In a method of maintaining substantially at a predeterminedtemperature the storage compartment of a double-shell type refrigeratorcar having the compartment spaced by interconnecting air passagewaysfrom the inner surfaces of the outer shell and having'refrigerantsdisposed in overhead tanks beneath the roof of the car adjacent thestorage compartment, the outer surfaces ofthe refrigerant tanks being inheat exchange relationship with air flowing through said passageways,wherein air is drawn in symmetrical patterns about the sidewallperiphery of the storage space, then withdrawn to each end of the car indivergent streams, and circulated vertically about the ends` of the carin A 'symmetrical patterns, the steps comprising directing the thuscirculated air streams con-v vergently above the storage compartment andsimultaneously vpassing the streams into a plurality' of heat exchange"zones of progressively diminishing temperatures to chill the air, anddrawing off transversely and peripherally predetermined portions from'the convergent air streams at spaced intervals whereby each stream isthus substantially distributed peripherally prior to convergence. Y

4. The method of refrigerating the storage compartment of a refrigeratorcar having the compartment spaced by air passageways from the innersurfaces of theends, side walls, roof and bottom of the car, the airpassageways being in communication vwith the compartment, and havingrefrigerants disposed in overhead tanks beneath the car roof andadjacent the storage compartment, the outervsurfaces of the refrigeranttanks being inl heat exchange relation with air flowing through the saidair passageways, which comprises: drawing air transversely insymmetrical patterns about the side Wall periphery of the storagecompartment; withdrawing said peripherally circulated air to each end ofthe car in divergent streams; circulating the longitudinally directedair streams vertically about the ends of the car in symmetrical patternsinto heat exchange relationship with a ceiling refrigerant disposed, atthe ends of the car; directing the chilled air convergently above thestorage compartment; diverting a portion of the chilled air laterallyand peripherally into the side wall air passageways; passing the balanceof the convergent air streams into heat exchange relationship with aninwardly disposed ceiling refrigerant of lower temperature than saidfirst mentioned refrigerant and diverting another portion of saidfurther chilled air laterally and peripherally of thestoragecompartment.

5. The method of refrigerating the storage compartment of avrefrigerator car havingthe compartment spacedby air passageways from theinner surfaces of the ends, side walls,roof and bottom of the car, thesaid air passageways interconnecting the compartment and car, Vandhaving refrigerants disposed in the overhead tanks beneath the car roofand adjacent the storage compartment, the outer surfaces of therefrigerant tanks vbeing in heat exchange relation with air flowingthrough the said air passageways, which comprises: causing air to flowin symmetrical patterns about the side wall periph-` ery of the storagecompartment through the air passageways; directing said peripherallycirculated air to each end of the car in divergent streams; circulatingthe longitudinally directed air streams vertically about the ends of thecar in symmetrical patterns into heat exchangerela- 9 tionship with afirstv overhead refrigerant disposed at the ends of the car; directingthe chilled air convergently above the storage compartment andconcurrently diverting a portion of the chilled air laterally andperipherally into the side wall air passageways; passing the balance ofthe convergent air streams into heat exchange relationship with aplurality of inwardly disposed overhead refrigerante of progressivelydiminishing temperature lower than the temperature of said firstmentioned refrigerant and concurrently diverting other portions of saidfurther chilled air laterally and peripherally of the storagecompartment; and recirculatingl the entire iiow of chilled air thusperipherally distributed about the storage compartment wherebyrecirculated air dissipates to the refrigerants heat conducted into thecar from the outside atmosphere.

6. A railroad refrigerator car comprising: a storage compartment, thecompartment being spaced by air passageways from the'inner surfacesofthe ends, side walls, roof and bottom of the car, the air passagewaysbeing interconnected and being in communication with the upper portionof the compartment, a plurality of tanks containingr low temperatureeutectic brine refrigerant disposed beneath the car roof and adjacentthe storage compartment, the outer surfaces of the refrigerant tanksbeing in heat exchange relationship with the Vair flowing through saidpassageways, pipe drains interconnecting the tanks in series from thecentermost tanks to each end of the car whereby brine melted in thecentermost tanks will flow outwardly to the ends of the car throughtanks intermediate thereto; and air impelling means disposed incommunication with the air passageway for forcing divergent streams ofair toward the opposite ends of the car and through the saidpassageways.

7. A. double-shell type refrigerator car com,- prisng a storagecompartment spaced by air passageways from the inner surfaces of theends, side walls, roof and bottom ofthe car, the air passageways beinginterconnected and being in communication with the upper portion of thecompartment, air impelling means for circulating streams of air aboutthe periphery of the compartment through the air passageways, overheadtanks spaced apart longitudinally containing eutectic brine mixturerefrigerants disposed f beneath the roof of the car adjacent the storagecompartment, and pipe drains interconnecting the centermost tank `oneach side of the middle of the car with the tanks intermediate the endswhereby brinev melted in the centermostvtanks will iiow outwardly to theends of the car through the tanks intermediate thereto.

8. A double-shell type refrigerator car comprising a storage compartmentspaced by air passageways from the inner surfaces of the ends, sidewalls, roof and bottom of the car, the air passageways beinginterconnected and being in communication with the upper portion of thecompartment, air impelling means for circulating streams of air aboutthe periphery of the ccmpartment through the air passageways, overheadtanks spaced apart longitudinally containing eutectic brine mixturerefrigerants disposed beneath the roof of the car adjacent the storagecompartment, and pipe drains interconnecting the centermost tank on eachside of the middle of the car with the tanks intermediate the endswhereby brine melted in the centermost tanks will flow outwardly to theends of the car through the tanks intermediate thereto, thetemperatures- `most tank on each side of the longitudinal center of thecar with the tanks longitudinally outwardthereof, said' center-mosttanks containing a eutecti'c mixture of sodium chloride, ammoniumnitrate and ice, and said outward tanks containing aeutectic mixture ofwater ice and salt, whereby as iceI ini the centermost tanks melts theresultant brine containing a eutectic concentration of ammonium nitra-tefiows outwardly to the ends of the" car through the outward tanks andthereby distributes an effective concentration of ammonium nitrate tothe outer tanks, and air impelling means for circulating streams of airabout the longitudinal and transverse periphery of the compartmentthrough the air passageways and in heat exchange contact with thesurfaces of said tanks.

l0. The method of refrigerating the storage space of a refrigerator carhaving the said space separated by air passageways from the innersurfaces of the ends` of thev car, from the inner surfaces of the sidewallsl and from the bottom and r-oof, the said passageways beinginterconnected with the said storage space, the car having refrigerantsdisposed in overhead tanks beneath the roof, the outer surfaces of whichare in heat exchange relation with air flowing through the saidpassageways, such flow of air being induced by a fan' actuated by therunning gear of the car, which comprises: causing air to fiow throughthev passageways between storage space and the inside walls of the car,further causing such air to flow to each end of the car, circulatingsaid streamsvertically about the ends of the car in heat, exchangerelationship with a first refrigerant inl overhead tanks at the ends ofthe car beneath the roof; directing the chilled air above the storagecompartment, diverting said chilled air into the side wall flues betweenthe storage compartment and the inner side walls of the car whilecausing a portion thereof to pass in direct heat exchange relationshipwith a plurality of centerwardly disposed refrigerants in overhead tanksof progressively diminishingtemperature lower than the temperature ofthe refrigerant in the said end overhead tanks, and recirculating theentire ow of chilled air passing through the side wall ilues whereby thesaid recirculatedair dissipates to the refrigerante the heat conductedinto the car from the outside atmosphere.

11. .A double shell type refrigerator car system, comprising a storagecompartment spaced by air passageways from the inner surfaces of thecar, a plurality of overhead tanks extending transversely of the car andspaced apart longitudinally of the car containing heat transfer fins ontheir surfaces, and pipe drains connecting the centermost tank on eachside of the longitudinal center of the car with the tanks longitudinallyoutward thereof, saidl centermost tanks being supplied with an eutecticmixture of sodium chloride, ammonium nitrate and water ice, and saidoutward tanks being supplied with an eutectic mixture of water ice andsalt, whereby as the ice in the centermosttanks melts, the resultantbrine conthe said outer tanks, and air impelling means for circulatingstreams of air about the storage compartment and in heat exchangecontact with the surfaces of the said tanks and the said heat transferfins.

12. A double shell type refrigerator car system, comprising a storagecompartment spaced by air passageways from the inner surfaces of thecar, a plurality of overhead tanks extending transversely of the car andspaced apart longitudinally of the car, and pipe drains connecting thecentermost tank on each side of the longitudinal center of the car withthe tanks longitudinally outward thereof, said centermost tanks beingsupplied with an eutectic mixture of sodium chloride, ammonium nitrateand water ice, and said outward tanks being supplied with an eutecticmixture of water ice and salt, whereby as the ice in the centermosttanks melts, the resultant brine containing a eutectic concentration ofammonium nitrate flows outwardly to the ends of the car through theoutward tanks, thereby distributing an effective concentration ofammonium nitrate to the said outer tanks and substantially lowering thetemperature in the outward tanks, and air impelling means forcirculating streams of air about the storage compartment and in heatexchange contact with the surfaces of the said tanks, said air firstcontacting the outermost tanks containing the brine of highesttemperature, and lastly contacting the centermost tanks containing thebrine of lowest temperature.

13. A double shell type refrigerator car system, comprising a storagecompartment spaced by air passageways from the inner surfaces of thecar, a plurality of overhead tanks extending transversely of the car andspaced apart longitudinally of the car, and pipe drains connecting thecentermost tanks on each side of the longitudinal center of the car withthe tanks longitudinally outward thereof, said centermost tanks beingsupplied with an eutectic mixture of sodium chloride, ammonium nitrateand water ice, and said outward tanks being supplied with an eutecticmixture of water ice and salt, whereby as the ice in the centermosttanks melts, the resultant brine containing an eutectic concentration ofammonium nitrate flows outwardly to the ends of the car through theoutward tanks, thereby distributing an effective concentration ofammonium nitrate to the said outer tanks, whereby temperature of thebrine in the centermost tanks is lower than in the outermost tanks, andair impelling means for circulating streams of air about the storagecompartment and in heat exchange contact with the surfaces of the saidtanks, said air first contacting the outermost tanks containing thebrine of highest temperature, and lastly contacting the centermost tankscontaining the brine of lowest temperature, the surfaces of said tanksbeing provided with heat transfer fins in contact with the circulatingair to increase heat transfer.

14. The method of cooling air in a closed compartment having a pluralityof interconnecting low temperature liquid refrigerant tanks ofdifferential temperatures comprising drawing a continuous ilow of airabout the inner surfaces of the compartment, thereby gathering into thecirculating air now heat conducted into the compartment from theoutside, directing the air flow successively first into heat exchange'contact-with the higher temperature refrigerant tank and then with thelower temperature refrigerant tank, thereby supplementing the coolingeffect of said first heat exchange contact, and concurrently drawingmelted brine from the refrigerant tank of lower temperature into andthrough the tank of higher temperature, thereby maintaining a balanceddifferential temperature relationship therebetween.

15. In a method of cooling air to a temperature of 0 F. or less in aclosed compartment having a plurality of brine refrigerant tanks ofdifferential temperatures wherein the higher temperature refrigerant iswater ice and the other lrefrigerant is provided with a eutectic mixtureof water ice and a melting point depressant, the tanks beinginterconnected by pipe drains, the steps comprising directing a forcedcirculation of air successively into heat exchange contact first withthe refrigerant of higher temperature and then with the refrigerant oflower temperature, and draining melted brine from the lower temperaturerefrigerant into and through the higher temperature refrigerant.

16. In a method of cooling air to a temperature of about 0 F. in aclosed compartment having a plurality of brine refrigerant tanks ofdifferential temperatures wherein the lower temperature refrigerant isprovided with a eutectic mixture of ammonium nitrate, salt and waterice, and the other refrigerant being provided with a eutectic mixture ofsalt and water ice, the tanks being interconnected by pipe drains, thesteps comprising directing a forced circulation of air successively intoheat exchange contact with the refrigerant of higher temperature andthen with the refrigerant of lower temperature, and drawing the meltedbrine from the lower temperature refrigerant into and through the highertemperature refrigerant.

17. The method of cooling air to a temperature of 0 F. or less in aclosed compartment having a plurality of interconnected brinerefrigerant tanks wherein the tank of lowest temperature is providedwith a eutectic mixture of ammonium nitrate, salt and water ice whichmelts at 15 F. and the other tanks being provided with a eutecticmixture of salt and water ice which melts at .-5" F., the stepscomprising directing a forced circulation of air successively into heatexchange contact first with the tanks of higher temperature and thenwith the tanks of lower temperature, and draining melted brine from thetank of lower temperature successively through the other tanks therebyreducing the temperature in the tanks of higher temperature and lowerconcentration of ammonium nitrate to about -12 F. while providing anaverage temperature of the brine in all of the tanks of about 13 F.,with consumption of not more than about 5% ammonium nitrate on ice.

ROBERT D. PIKE.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 1,219,570 McCoy Mar. 20, 1917 1,344,057 Moore June 22, 19201,421,913 Collins July 4, 1922 2,324,749 Wieden July 20, 1943 2,331,002Small Oct. 5, 1943 2,501,141 Plummer Mar. 21, 1950

